Exploring integrative approaches to understand the interaction of microbial biofilms and fluid chemistry on larval settlement at deep-sea hydrothermal vents

Hydrothermal vents provide ephemeral habitats for deep-sea fauna that rely on chemosynthesis for their livelihood. Biologists have long proposed that the chemical compositions of vent fluids serve as settlement cues for vent-dependent fauna to colonize vents along mid-ocean ridges; however, this hypothesis remains largely untested. In addition, microbial community composition in vent fluids and the development of microbial biofilms at vent openings would be expected to vary in response to vent fluid chemistry, and may facilitate or inhibit the settlement of invertebrate species. A major objective of our research is to understand biological/geochemical interactions during initial colonization of basalt at deep-sea hydrothermal vents, through time-series studies that combine molecular genetic characterization of colonists and in situ measurements of fluid chemistry. We performed an interdisciplinary pilot study of the microbial and invertebrate species colonization of basalt panels in conjunction with co-located, in situ, time-series detection of dissolved H2, H2S, pH, and temperature at a hydrothermal vent on the East Pacific Rise. Our study involved deploying and recovering a series of settlement panels in close proximity to an in situ chemical sensor for 3- to 9-day time periods. The settlement panels were preserved in situ, and the bacterial and archaeal species diversity in developing biofilms is being analysed. Small recovered colonists, that are not amenable to species identification based on morphology, are identified using molecular methods developed at WHOI. We will gain fundamental insights into how hydrothermal fluid chemistry and microbial biofilms affect larval settlement on basalt substrates, the first step in larval recruitment and the ultimate development of megafaunal assemblages at vent sites. Recently a volcanic eruption occurred at the 9N deep-sea hydrothermal vent site on the East Pacific Rise, providing a unique opportunity to study microbial colonization after a major natural disturbance, and it will be very interesting to compare this with the experimental work.

The pilot study was funded by the WHOI Deep Ocean and Exploration Institute, and ongoing work in my laboratory looking at microbial colonization in response to the recent eruption is funded by NSF.